Polymeric films are useful in a variety of disparate technical applications. For example, polymer films are often used in display applications to provide a variety of optical functions to the display. One polymer material that is often incorporated as an optical film of a display device is triacetyl cellulose (TAC) film. Illustratively, TAC films may be used as polarizer protective layers in optical polarizers commonly used in liquid crystal displays (LCDs). The fundamental lack of TAC polymer orientation combined with the low stresses of solvent casting forms a unique polymer system for extremely isotropic LCD coversheets. These fundamental advantages have allowed solvent cast cellulose triacetate to capture the vast majority of LCD coversheet applications.
However, the TAC is a soft film and when produced and rolled for storage, or transportation, or both, the smooth front and back film surfaces have a tendency to stick or block together and generate poor wound roll quality which leads to defects in the LCD protective layers. In fact, similar films with smooth surfaces tend to ‘block’ or stick together when stacked or rolled. This is particularly troublesome when rolled substrates are stored at high temperatures and humidity.
Anti-blocking or slip agents have long been known to provide surface roughness to prevent adhesion between two sheets of what would otherwise be smooth film surfaces. The effect of roughening the surface is to reduce the frictional forces between the surfaces of sheets or layers of the substrate. Many inorganic and polymeric materials are known to act as good anti-blocking agents and various solutions to the problem have been proposed. Unfortunately, the surface roughness increase of the polymeric film via the anti-blocking agents is garnered at the expense of film haze or increased light scattering characteristics of the films.
Another source of optical degradation in optical films have anti-blocking agents is the anti-blocking agents themselves. To this end, the anti-blocking agents are often individual particles disposed in the polymeric film to provide the desirable surface roughness. However, if the size of the individual particles is in the realm of the wavelength of light, or if the individual particles flocculate and attain a size that approaches the wavelength of light, optical scattering occurs and the optical properties are deleteriously impacted.
In view of the foregoing, there exists a need to provide optical films having anti-blocking properties that overcome at least the shortcomings of known films described above.